Electric heat pumps have become common means for heating and cooling indoor spaces. Such units typically employ direct expansion of refrigerants such as CFCs and HCFCs. They typically position a compressor and condensor coil in the ambient environment, where the condensor may be exposed to ambient air, usually by use of a fan. The other component of the system comprises an evaporator coil which is positioned in the indoor space, and which transfers heat to and from the indoor air circulated over the coil. As is well known in the art of heating and refrigeration, the heat pump heats indoor spaces by transfering sensible heat from the ambient atmosphere to the indoor air, while when desired, it cools indoor spaces by transfering heat from the indoor air to the ambient (in the same manner as a conventional air conditioner. Typical heat pumps also employ a resistive heating coil for supplementation of the heating function when ambient temperatures are too low to permit the desired heating.
Regenerative type periodic flow devices are conventionally employed for the transfer of heat or a material from one fluid stream to another, and thereby from one area or zone in space to another. Typically, a sorptive mass is used to collect heat or a particular mass component from one fluid stream which flows over or through that mass. The flowing fluid is rendered either cooler (in the case of heat sorption) or less concentrated (in the case of, for instance, adsorption of particular gases). The sorptive mass is then taken "off-stream" and regenerated by exposure to a second fluid stream which is capable of accepting the heat or material desorbed with favorable energetics.
In some applications continuous flow systems are used, where the sorptive media itself is moved between two or more flowing fluid streams. The most common construction employed for such systems is a porous disk, often referred to as a wheel or rotor. In its simplest form, such a wheel is divided into two flow zones, and fluid is passed over the sorptive surface of the wheel (typically flowing through the thickness of the disc parallel to the rotational axis of the cylinder) as the wheel is rotated to carry the sorptive material from one zone, into the other, and back again to complete a revolution. In a heat exchanger wheel, for instance, one zone of warm fluid and one zone of cooler fluid are present. Heat is adsorbed by the material of the wheel in the warm flow zone, and is carried away from the wheel as the sorptive material passes through the cool flow zone.